1. Field of the Invention
The present invention relates to a package containing a roll of a long electrode plate for storage.
2. Description of the Related Art
In recent years, reduction in size and weight of electronic equipment and communication equipment has rapidly been advanced. This advance has also required reduction in size and weight of secondary batteries used as driving power sources for these equipments. For these demands, there have been developed nonaqueous electrolyte secondary batteries having high energy density and high voltage, typically, a lithium ion secondary battery, in place of conventional alkaline batteries.
A positive electrode plate and a negative electrode plate have large influence on the performance of the secondary battery, thus it is emphasized to reduce the thickness and enlarge the area of the electrode plates to be wound in the battery in order to elongate the life span of a charge/discharge cycle, and to have high energy density.
In the production of such an electrode plate, for example, as shown in FIG. 1 (herein, FIG. 1A is a plan view, and FIG. 1B is a side view.), an active material layer having a function of emitting lithium ions (i.e., a positive electrode plate) or an active material layer having a function of adsorbing these lithium ions (i.e., a negative electrode plate) is formed on a collector made of an aluminum foil, a copper foil or the like. There is provided a portion wherein the active material layer is not formed (a portion wherein the electrode plate is exposed) as a portion to which a terminal is to be connected in a pattern form.
The electrode plate is cut along a dotted line as shown in FIG. 1A, and divided into a long plate form of a width corresponding to the size of a battery to be finally assembled, as shown in FIG. 2. Herein, a long plate form refers to a thin flat tape-like form. An interval between the plural portions to which the terminals are to be connected on the long electrode plate is decided in accordance with the size of a battery to be finally assembled.
The positive or negative long electrode plate is, for example, a long plate having length of about 200 to 500 m in the direction of conveyance (in longitudinal direction), and is wound in a rolled form to be handled in a discal state which has, for example, an outside diameter of about 20 to 40 cm, and the thus wound long plate is used in an assembling step of the battery.
Both positive and negative long electrode plates are released from a roll, and cut in a certain length. In the assembling step of the battery, the positive long electrode plate and the negative long electrode plate are rolled together disposing a separator therebetween, and contained in a battery case for use. In such a process of producing a long electrode plate through an assembling step of the battery, there is a strict condition that the moisture absorption of the electrode plate should be completely prevented since the moisture absorption of the electrode plate causes deterioration of the electrode performance and increase in thickness of an active material layer so that an electrode plate cannot be contained inside of a battery of a certain size. Also, other problems besides the moisture absorption often occur such as heating generation due to electrical short-circuit, which occurs when an electrode plate receives an external collision or is put straight to store or transfer in a rolled form and damaged near grounding by its own weight. In order to overcome these moisture absorption and damage problems, conventionally, a wide long electrode plate has been produced to cut in a certain width, the long plate is wound in a rolled form and subjected to vacuum drying, and then the wound plate has been stored in a airtight container such as a plastic bag, and it has been transported in this state, until the assembling step of the battery has been carried out. The assembling step has been carried out in a room the atmosphere of which was kept in a dried condition.
Further, it is not limited to the electrode plate for the lithium-ion battery, but also an electrode plate for an electric double layer capacitor, an electrode plate for a fuel cell or the like are handled in a state, as shown in FIG. 3 (herein, FIG. 3A is a plan view, and FIG. 3B is a side view.), that an electrode plate, which has an active material layer formed on one surface of a long (consecutive) collector (an electrode substrate), is continuously wound to a take-up core. The electrode plate is cut along a dotted line, as shown in FIG. 3A, in a plate form of a width corresponding to the size of a battery to be finally assembled, as shown in FIG. 4, and a terminal is connected on an opposite surface of the collector wherein the active material layer is formed to be used accordingly.
In carrying out the above method, when a roll of a long electrode plate is contained or conveyed, for example, as shown in Japanese Patent Application Laid-Open (JP-A) No. 10-69899, the roll of a long electrode plate is fixed to be contained in a sealed container having a tape pulling-out opening formed. The tape pulling-out opening of the sealed container is sealed with a sealing seal. A core of the roll of a long electrode plate and a side plate of the sealed container are fixed with the use of a bolt which is a side plate fastening means by a screw cramp wherein an inside diameter of the core and the bolt intermesh.
However, when using the above sealed container, there is a problem that it takes a lot of trouble with axial rotation of the fastening means of the bolt in a bore of the core.
It is mentioned in JP-A No. 10-69899 that the fastening means of the bolt may be pushed inside of a core without rotating the fastening means of the bolt, however, in the packing form using the sealed container as mentioned above, the sealed container is not discarded when it is used once. Packing members are expensive and based on the premise that after the members are used once, the members are collected for reuse. Thus, there is a problem that if a long electrode plate is transported abroad in a packing form of a roll of a long electrode plate, it is particularly costly to collect the packing members.
Also, an electrode plate contained in a sealed container disclosed in JP-A No. 10-69899 is used by connecting the roll of an electrode plate kept in the sealed container on an electrode take-up device and rotating the roll of an electrode plate.